145 is the section width. The wheels are obviously 10 inch. So a Mini tyre will not fit as it fouls on the suspension casting. I have had cars with spacers to get round this but they still catch the wheel arch, put extra strain on the wheel bearings, and of course a spacer on the rear wheel means its no longer central. Does the car run well on radials. Yes, up to a point, but the extra drag of the tyres slows down speed, and you have no warning of handling issues, as the level of grip is so much increased. On the smaller crossplys you tend to hear the tyres scuffling and that is a clue to back off. I think the car is better off radials, unless they be suitably narrow section.
There used to be a Kings tyre and a Bridgestone, both 4.00 by 10, that fitted OK, but the section, though bulking up well, is narrow. I believe HTC Ltd uses Uwe Staufenburg to resource tyres, as the Goggo saloon shares the size. HTC Ltd seems to have lost the thread a little, as they have not published rally details either, unlike them. I would have been seeing Nick Haddon this evening, who does their spares, but I am buying and moving Appleton Rutherford Labs library shelving tonight, bargain. I believe the Mem Sec is one Grant Kearney, contributor to this Forum?